1. Field
Embodiments of the disclosure relate generally to the field of vibration reduction systems for aircraft and more particularly to a plurality of tuned mass dampers having viscous damping and mounted in multiple locations on the airframe with directional orientation determined to maximize damping of primary modes of aeroelastic limit cycle oscillation.
2. Background
Large modern commercial jet aircraft are designed with consideration of the aeroelastic stability of the aircraft. However, in certain cases aeroelastic designs may be subject to resonant oscillations created under certain aerodynamic conditions and at various speeds. Such oscillations can be localized in certain portions of the airframe or may be whole airframe aeroelastic modes including limit cycle oscillations (LCO) involving the nacelles, wing and fuselage.
To minimize LCO, prior art aeroelastic solutions include payload and/or fuel restrictions, active modal suppression using control surfaces, adding ballast, vortex generators to change aerodynamic flow characteristics and structural changes (such as adding wing stiffness). Payload or fuel restrictions will typically reduce capability of the aircraft while active modal suppression requires extensive design and experimentation resulting in extended design lead time and may also affect performance. Use of ballast results in a significant increase in weight which may affect performance and may drive structural changes and inherent structural changes for stiffness also typically add weight. Vortex generators, while often effective for localized oscillation suppression are not typically effective for full airplane LCO
It is therefore desirable to provide modal damping to satisfy aeroelastic stability and vibration requirements with low cost, simple design elements with minimized weight increase and no performance impact.